Pickup Truck Stamps

These nifty-looking pickup truck stamps are just out at the post office. I bought a book of them the other day because they looked so nice. Too bad they're the stick-on kind and will not last past a year or two before the glue wears through the front of them. Stamps used to be collectible, but not anymore. I wonder why the post office would throw away such a good source of revenue as collectors?